Severe protein-energy malnutrition, a common complication in patients with advanced liver disease, negatively influences clinical evolution and survival, while appropriate nutritional intervention has been found to improve liver function and prognosis. Although the importance of nutritional factors has been greatly emphasized in the last decade, nutritional therapy remains a controversial issue in clinical hepatology. Because a considerable heterogeneity exists among patients regarding both nutritional needs and the pathophysiology of malnutrition, adequate assessment of nutritional status is mandatory to identify the type and the degree of malnutrition for the individualization of therapy. In this paper we first summarize the pathophysiology of malnutrition and the principles for the assessment of nutritional status in patients with chronic liver disease. We then offer rational, cost-conscious recommendations for therapy, with special emphasis on the role of nutritional support in the prevention and treatment of several complications.